Abell 31

Abell 31 is an ancient planetary nebula in the constellation of Cancer. It is estimated to be about 2,000 light years away. The central white dwarf has a spectral type of DAO.
Abell 31 is mainly composed of hydrogen and oxygen gas. The blue oxygen occupies the central region and makes up the bulk of the nebula, while the red hydrogen makes a ring at the nebula's edge. This object is very old, and consequently, it is very large and dim, and its gas is dispersing into the interstellar medium.
Some astronomical objects that appear nearby from our perspective include star clusters Messier 44 and 67, and galaxies NGC 2731 and IC 523, among many others.